/Engine/Source/Runtime/Engine/Classes/Materials/MaterialExpressionStrata.h
class UMaterialExpressionStrataAdd : public [UMaterialExpressionStrataBSDF](API\Runtime\Engine\Materials\UMaterialExpressionStrataBSDF)
FExpressionInpu...
A
Substrate material
FExpressionInpu...
B
Substrate material
uint32:  1
bUseParameterBlending
Merge A and B into a single material by mixing their inputs rather than their evaluation.